From his seat in a boat on the Santa Rosa Estuary, near Ecuador's southern port of Machala, biologist Francisco Freire motioned toward the green wall of mangroves lining the nearby bank.

"They're like a curtain, behind which are the shrimp farms," he said. Soon after he spoke, a gap appeared in the mangroves providing a glimpse of the barren scene behind the foliage - low walls of earth separating massive shrimp pools.

It is a common landscape along Ecuador's coast, where the area dedicated to shrimp farming has increased six fold since 1980 to cover more than 175,000 hectares (432,434) acres. Most of that expansion was at the expense of mangrove forests, but Freire is working with local fishermen to turn back the tide of destruction. He is helping them protect mangroves for the sustainable harvest of the shellfish that live on and around their roots.

Though establishing new shrimp farms has been prohibited in Ecuador for several years, more than a quarter of the country's mangroves have already been destroyed. During the 1980s and 1990s, shrimp exports were one of the country's top earners, but a series of viral diseases has ravaged the industry in recent years, driving many farms bankrupt.

In an attempt to repair some of the damage, Freire has helped two fishing cooperatives facilitate mangrove restoration on former shrimp farms. Through a project funded by the Global Environment Facility's Small Grants Programme, implemented by the United Nations Development Programme, the fishermen are managing those areas for sustainable shellfish production.

Shrimp are one of Ecuador's luxury exports. In 1999, the Ecuadorian shrimp export industry was worth US$870 million annually.

(Photo courtesy Noe Aquaculture Consultants)

They have traditionally gathered clams and mussels from the entire estuary, but shrimp farm expansion contributed to a decline in all local fisheries, since so many marine species depend on mangroves for at least part of their development. "Fifteen years ago, one fisherman could collect about 500 mussels per day. Now, a man is lucky to find 100," said Lucio Cacao, president of one of the cooperatives participating in the project.

Freire explained that the local Port Authority gave the cooperatives custody of two tracts of mangroves on the condition that they preserve them. Using techniques developed in Spain, the fishermen are increasing clam and mussel populations within their areas for eventual commercial harvesting.

Cacao said the 120 hectare (296 acre) area his cooperative manages was a shrimp farm that went broke after floods destroyed its dikes. Because mangrove forests are extremely resilient, much of the farm reverted back to its natural state. Upon gaining custody of the area, the fishermen broke down remaining dikes so that the tide could spread mangrove seeds over the mudflats. They also planted mangroves on 18 hectares (44 acres) that were not regenerating naturally.

Under the direction of Freire, the fishermen have erected screen barriers to keep their mollusks from migrating to other parts of the estuary. They have also stocked their areas with small bivalves collected elsewhere, or purchased with funds from the GEF Small Grants Programme. Once the shellfish populations reach a certain size, they can begin a sustainable harvest. An important component of the project is lowering predation. Since the biggest predator is man, each cooperative has built a guardhouse that members take turns staying in, to prevent other fishermen from filching their clams.

Though the mollusk populations are still recuperating, Freire believes they will be able to start harvesting commercially soon. The fishermen have traditionally depended on middlemen to market their shellfish, but recently they received training to help them market the shellfish directly to restaurants, which will further boost their incomes.

"We want this to become a small business," said Cacao. "We see it as something to pass on to our children."